CRYSTALLIZATION OF THE CHAPERONE PROTEIN SECB

The secretory protein SecB found in Escherichia coli is a molecular ch aperone that binds to precursor forms of a number of proteins targeted for export to the periplasmic space. SecB maintains these proteins in a translocation-competent conformation facilitating the translocation process. The material has been cloned and expressed in E. coli. Cryst als have been grown from polyethylene glycol 8000 by vapor diffusion u sing the hanging drop technique. These crystals are monoclinic, belong ing to space group C2 with unit cell dimensions a = 56.0 Angstrom, b = 111.1 Angstrom, c = 134.7 Angstrom, and beta = 104 degrees. The cryst als diffract to 8 Angstrom resolution on a Rigaku imaging plate detect or. Dynamic light scattering experiments suggest that SecB exhibits ag gregation behavior with a number of different precipitating agents. Th ese results may explain resistance of SecB to forming ordered crystals .